1. Technical Field of the Invention
The technical field of this invention relates to an air assisted fuel injection system for an internal combustion engine and more specifically a sequentially operating dual stage air metering valve including dual valves on a common shaft.
2. Description of Related Art
Air assisted fuel injection systems are known in the engine art particularly concerning internal combustion engines. Also, the utilization of an air flow control device or a metering valve is known to regulated the flow characteristics to the fuel injectors. For example, an air assisted fuel injection system including a metering valve is disclosed in a Society of Automotive Engineers (SAE) Paper No. 92029. In this paper, the authors illustrate and describe an air flow control device which has an air inlet and two air outlets. The inlet is connected to a source of pressurized air sufficient to cause a flow to the control device. One air outlet is connected to an inlet associated with an air assist type fuel injector. A second air outlet is connected the intake manifold of an internal combustion engine. Air supplied through the one outlet flows directly past the fuel outlet of the injector and so envelopes the spray pattern of fuel from the fuel injector. Air supplied through the second outlet flows into the intake manifold and subsequently mixes with the fuel introduced by the fuel injector.
The above identified SAE Paper No. 92029 describes a particular control valve design. As stated in the paper, the use of an air flow to a fuel injector assists in homogenation of fuel with air and also helps provide a desired fuel spray pattern. A beneficial results may be a reduction of hydrocarbons in the exhaust, a driveability improvement especially during transient conditions, and an engine performance improvement especially at an idle condition.
A three-stage flow control device is disclosed in the SAE Paper including a construction with a shaft movable axially in response to a selectively energized actuator device. The flow control device has two valve elements affixed to the shaft at spaced locations. Each valve element engages a valve seat when the shaft is in a first position. An air inlet means of the flow control device enters the housing at a place located between the two valve elements and valve seats. An outlet means is located opposite one of the valve elements and its seat and another outlet means is located opposite the other of the valve elements and its seat.